Newbie asking about sizes

Hi,

I wanted a Vitus Dee 29 in 19″ frame but it seems this is sold out. I’m 5’8″, can I get a 16″ frame one or will that be too small? Or would I be better off sacrificing the better brakes – Dee has mechanical disc and Vee has V-brakes – and going with a 19″ Vitus Vee 29? Or should I sacrifice the wheel size? I’ve been told 29ers were great for city riding though so I had my heart set on 29. Bike will be used 3 times a week in London where it is mostly flat.

Thanks for any help, I’m brand new at this!